function setImagePreview(){
                    var docObj=document.getElementById("filename");
                    if(docObj.files && docObj.files[0]){
                        //火狐下，直接设img属性
                        jQuery("img").attr("style","display:block");
                        jQuery("#cropbox").attr("width","240");
                        jQuery("#cropbox").attr("height","180");                   
                        //火狐7以上版本不能用上面的getAsDataURL()方式获取，需要一下方式  
                        jQuery("img").attr("src",window.URL.createObjectURL(docObj.files[0]));
                        jQuery("#p").val(imgSrc);
                     }else{
                         //IE下，使用滤镜
                        docObj.select();
                        var imgSrc = document.selection.createRange().text;
                        var localImagId = document.getElementById("cropbox");
                        var localImag120 = document.getElementById("img100");
                        //必须设置初始大小
                        localImagId.style.display = "block";
                        localImag120.style.display = "block";
                        localImagId.style.width = "240px";
                        localImagId.style.height = "180px";
                        //图片异常的捕捉，防止用户修改后缀来伪造图片
                        try{
                               localImagId.style.filter="progid:DXImageTransform.Microsoft.AlphaImageLoader(sizingMethod=scale)";
                               localImagId.filters.item("DXImageTransform.Microsoft.AlphaImageLoader").src = imgSrc;
                               localImag120.style.filter="progid:DXImageTransform.Microsoft.AlphaImageLoader(sizingMethod=scale)";
                               localImag120.filters.item("DXImageTransform.Microsoft.AlphaImageLoader").src = imgSrc;
                               jQuery("#p").val(imgSrc);
                            }catch(e){
                               alert("您上传的图片格式不正确，请重新选择!");
                               return false;
                           }
                        //alert(imgSrc);
                        //jQuery("img").attr("style","display:block");
                        //jQuery("#cropbox").attr("width","240");
                        //jQuery("#cropbox").attr("height","180");
                        //jQuery("img").attr("src",imgSrc);
                        //jQuery("#p").val(imgSrc);
                        document.selection.empty();
                    }
                }